They signed The Giving Pledge, the four-year-old brainchild of Bill Gates and Warren Buffett in which the world's wealthiest individuals promise to give away half or more of their money to charity before or after they die.

With the seven who signed on today, 128 wealthy families have made this commitment.

The truth is, many of these wealthy individuals have already set up charitable foundations before they sign the pledge. That's true of the tech billionaires that signed the pledge this week.

For instance, Eric Lefkofsky's wife, Liz, is the director of Lefkofsky Family Foundation. They support education, human rights, medical charities and the arts.

Bob Parsons and his wife Renee have the Parsons Foundation and they give money to charities around education, health care and quality of life, mostly in the Southwest.

Milner is known for investing in science. His foundation created something called The Fundamental Physics Prize where he awards up to $3 million to each scientist that wins it. In 2013, there were 9 winners and there are six nominees for 2014, with the final winners announced later this week. He also backed something called the Breakthrough Prize for the life sciences, along with Sergey Brin and Mark Zuckerberg (another billionaire who has signed the Pledge). That prize will give six winners $3 million apiece, too.